The present invention relates to a method and apparatus for ascertaining certain characteristics of tobacco, and more particularly to improvements in a method and apparatus for ascertaining the so-called filling power (resistance to compression) of tobacco. Still more particularly, the invention relates to improvements in ascertaining the filling power of tobacco which forms a continuous stream.
The filling power of tobacco is important to the manufacturers of cigarettes and/or smokers' products because it determines the weight of the mass of tobacco in a cigarette and hence the cost of the most expensive ingredient of such product. Attempts to improve or increase the filling power of tobacco include a variety of so-called puffing and analogous techniques many of which involve increasing the moisture content of tobacco particles and thereupon abruptly heating the soaked or otherwise wetted particles for the purpose of causing evaporation of moisture and attendant increase of the volume of tobacco. The extent to which the filling power of tobacco is increased must be monitored in order to ensure that the puffing operation can be adjusted if the extent to which the filling power is increased is outside of an optimum range. In the absence of reliable methods and apparatus for continuous monitoring of the filling power, puffing of tobacco particles can be regulated only sporadically. As a rule, conventional monitoring involves removal of batches of tobacco from the so-called primary processing equipment, introduction of a predetermined amount per weight into a cylindrical vessel, placing of a predetermined weight on top of the mass of tobacco in the vessel, and ascertaining the resulting reduction of the height of the compacted mass in the vessel. Such tests are normally carried out in a laboratory so that the results which are obtained thereby cannot be utilized for continuous regulation of the operation which involves increasing the filling power of tobacco in the processing plant proper.
In accordance with another prior proposal, filling power of tobacco is ascertained by monitoring the hardness of the fillers of cigarettes or analogous finished rod-shaped smokers' products. To this end, one selects a number of cigarettes having identical sizes, weights and shapes, and the cigarettes are placed under a weight to flatten the fillers to an extent which is proportional to or indicative of the filling power of tobacco forming the fillers. Of course, the outcome of such procedure is not truly indicative of the filling power of tobacco prior to conversion into smokers' products because the filler of a cigarette undergoes quite pronounced compression during the making of the cigarette, namely, during conversion of a trimmed tobacco stream into a rod-like filler in the wrapping mechanism of a cigarette rod making machine. The thus compressed filler is held against radial expansion by the web of cigarette paper which is draped therearound and whose longitudinally extending marginal portions are bonded to each other by a suitable adhesive to form a seam which must be sufficiently strong to prevent the wrapper of the rod from opening up and from thus permitting expansion of compacted tobacco particles.
This second procedure of ascertaining the filling power of tobacco also exhibits the drawback that the filling power is not ascertained continuously and at the location where the filling power can or could be immediately influenced if it deviates from an optimum value.
Apparatus for increasing the filling power of tobacco are disclosed, for example, in commonly owned U.S. Pat. No. 3,881,498 granted May 6, 1975 and in commonly owned U.S. Pat. No. 3,957,063 granted May 18, 1976.